21331487 has 2 divisors, whose sum is σ = 21331488. Its totient is φ = 21331486.

The previous prime is 21331477. The next prime is 21331523. The reversal of 21331487 is 78413312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21331487 - 2¹⁸ = 21069343 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21331477) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10665743 + 10665744.

It is an arithmetic number, because the mean of its divisors is an integer number (10665744).

Almost surely, 2^21331487 is an apocalyptic number.

21331487 is a deficient number, since it is larger than the sum of its proper divisors (1).

21331487 is an equidigital number, since it uses as much as digits as its factorization.

21331487 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4032, while the sum is 29.

The square root of 21331487 is about 4618.6022777459. The cubic root of 21331487 is about 277.3365084092.

Adding to 21331487 its reverse (78413312), we get a palindrome (99744799).

The spelling of 21331487 in words is "twenty-one million, three hundred thirty-one thousand, four hundred eighty-seven".